Silicon carbide (SiC) is a semiconductor having a band gap larger than that of silicon (Si), which has been conventionally widely used as a material for semiconductor devices, and is a so-called wide band gap semiconductor. By adopting silicon carbide as a material for a semiconductor device, the semiconductor device can have a high breakdown voltage, reduced on resistance, and the like. Further, the semiconductor device thus adopting silicon carbide as its material has characteristics less deteriorated even under a high temperature environment than those of a semiconductor device adopting silicon as its material, advantageously.
For example, WO 2010/098294 (Patent Document 1) discloses a silicon carbide semiconductor device including a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) cell. The silicon carbide semiconductor device includes: a silicon carbide semiconductor substrate; a drift layer provided on a main surface of the silicon carbide semiconductor substrate and having a first conductivity type; and a well layer provided to extend from an upper surface of the drift layer to inside of the drift layer, the well layer having a second conductivity type. The silicon carbide semiconductor device further includes a semiconductor layer having the second conductivity type. This semiconductor layer is formed on the upper surface of the well layer or an upper layer portion of the well layer.